Various surface treatment processes which confer desired characteristics to the surface of a substrate have been suggested. Many of these surface treatment processes were developed to provide corrosion resistance, lubricity, or a foundation for subsequent coatings or painting. For example, a surface of a substrate may be pre-treated prior to applying a coating layer (e.g., paint layer, lacquer layer, etc.) in order to improve not only the adhesive property between the surface and the coating layer, but also protection from severe and harmful elements.
SiO2 coating using conventional sol-gel processes is a widely used method for treating surfaces of substrates. However, applying a silica coating using conventional coating methods provides insufficient adhesion because of the inadequately generated surface roughness or surface area. Phosphating is another widely used surface treatment method. However, one drawback to the conventional phosphating process is that it changes the chemical composition of the surface of the substrate due to the involvement of acidic agents. Another drawback is that the conventional phosphating process is only applicable to limited types of metals.